This invention relates generally to a method for the gaseous reduction of particulate ores to metals in particulate form in a moving bed, vertical shaft reactor, and more particularly, to a method for the reduction of the ore and the cooling of the resulting metal particles using a reducing gas externally supplied from a solid or liquid fossil fuel gasification unit. This invention is particularly suitable to the reduction of iron ore to sponge iron and is illustratively described with particular reference thereto.
For purposes of describing the present invention the terms "reforming," "reforming zone," etc., specifically refer to chemical reactions whereby the H.sub.2 to CO ratio of the reducing gas supplied to the moving bed, vertical shaft reactor is increased.
In general, the production of sponge iron in a typical vertical shaft, moving bed reactor involves two principal steps, namely, reduction of the ore with a suitable hot reducing gas in a reduction zone of the reactor and then subsequent cooling of the resulting sponge iron with a gaseous coolant in a cooling zone of the reactor. The reducing gas is typically a gas largely composed of carbon monoxide and hydrogen injected into the reactor at temperatures in the range of 850.degree. C. to 1100.degree. C., preferably 900.degree. C. to 1000.degree. C. The hot reducing gas may be introduced into the reactor at the bottom of the reduction zone and passed upwardly through the reactor to flow counter-currently to the downwardly moving ore, or alternatively, the hot reducing gas may be introduced at the top of the reduction zone and caused to flow co-currently with the downwardly moving ore. It is well known in the art to cool the sponge iron by injecting a cooling gas at relatively low temperature into the cooling zone of the reactor and passing the cooling gas upwardly through the reactor whereby the cooling gas temperature is increased and the temperature of the sponge iron is reduced.
In previously proposed processes, the reducing gas used in the direct reduction of iron ores has been derived from a number of sources, e.g., the catalytic reforming of hydrocarbons and steam. Systems using natural gas and steam to generate a reducing gas require the use of catalytic reforming units. In prior processes where solid or liquid fuels are used to generate the reducing gas as opposed to those processes which utilize natural gas, additional equipment has been required to enrich the gas so that it may be effectively used for reduction purposes.